[DEV-1853] Add intervention config

[Lax125]

Description

See title. Also cleaned up the serialization of the config to JSON using short circuit magic.

Associated tasks

No blocking nor blocked tasks.

Test Steps

Run an intervention work package using the new config fields:

result = eas_client.run_hosting_capacity_work_package(
    ...,
    intervention=InterventionConfig(
        base_work_package_id="<base-work-package-id>",
        year_range=YearRange(2028, 2028),
        allocation_limit_per_year=5,
        intervention_type=InterventionClass.DVMS,
        dvms=DvmsConfig(
            lower_limit=0.94,
            upper_limit=1.1,
            lower_percentile=1.0,
            upper_percentile=99.0,
            max_iterations=4,
            regulator_config=RegulatorConfig(
                pu_target=1.0,
                pu_deadband_percent=2.0,
                max_tap_change_per_step=3,
                allow_push_to_limit=True
            )
        )
    )
)

Checklist

If any of these are not applicable, strikethrough the line ~like this~. Do not delete it!. Let the reviewer decide if you should have done it.

Code

• I have performed a self review of my own code (including checking issues raised when creating the PR).
  - [ ] I have added/updated unit tests for these changes, and if not I have explained why they are not necessary. (tested manually)
• I have commented my code in any hard-to-understand or hacky areas.
• I have handled all new warnings generated by the compiler or IDE.
• I have rebased onto the target branch (usually main).

Documentation

• I have updated the changelog.
• I have updated any documentation required for these changes.

Breaking Changes

• I have considered if this is a breaking change and will communicate it with other team members by posting it on the Slack breaking-changes channel.

No breaking changes---previously working work package configs will operate the same.

[ryanjcoleman]

Task linked: DEV-1853 Add intervention support to EAS Python client

[vincewhite]

lgtm